Extendible safety mechanism

ABSTRACT

An extendible safety mechanism for use with a lift truck having a body and an elevatable operator&#39;&#39;s station. The mechanism includes a switch mounted on the body and a control mounted on the operator&#39;&#39;s station. The control is connected to the switch by a pair of flexible tension members which are wound on a drum biased to exert a tension on the tension members and means for varying the effective length of one of the tension members. The ends of the tension members remote from the drum are connected to the ends of a bar which is mounted for pivotal movement about an axis intermediate the ends thereof and connected to the switch.

United States Patent l 13,572,468 [72] Inventor Henry J. Thomas [56] References Cited Battle Creek, Mich. UNITED STATES PATENTS 1 PP 857,401 3,416,109 12/1968 Gandolfo 200/161 1 Flled Sew-12,1969 3,424,271 1/1969 Michelson 182/148 [45] Patented Mar. 30,1971 I [73 Assignee Clark Equipment Company Primary Examiner-Reinaldo P. Machado Attorneys- Kenneth C. Witt, John C. Wiessler, Robert H.

Johnson and Reginald J. Falkowski ABSTRACT: An extendible safety mechanism for use with a lift truck having a body and an elevatable o erators station. [54] EXTENDIBLE T MECHANISM The mechanism includes a switch mounted 0 1 1 the body and a 8 Chums 6 Drawmg control mounted on the operators station. The control is con- [52] U.S.Cl nected to the switch by a pair of flexible tension members which are wound on a drum biased to exert a tension on the [51] Int. Cl E04g 1/18, tension members and means for varying the effective length of one of the tension members. The ends of the tension members [50] Field of Search remote from the drum are connected to the ends of a bar 141,112, 63; 74/892, 501.5; 200/161; l87/(Inquired) which is mounted for pivotal movement about an axis intermediate the ends thereof and connected to the switch.

Patented March 30, 1971 3 Sheets-Sheet 1 FIG. I

INVENTOR HENRY J. THOMAS ATTORNEY Patented March 30, 1971 3 Sheet s-Sheet 2 FIG. 4

Fl G. 3

INVENTOR HENRY J. THOMAS ATTORNEY Patented March 30, 1971 3 Sheets-Sheet 5 l I g .gg...9 vf-za &L .1

PL PM 96 :84V

"ONTROLS INVENTOR HENRY J. THOMAS ATTORNEY EXTENDIBLE SAFETY MECHANISM BACKGROUND OF THE INVENTION The field of art to which this invention relates includes machine elements and mechanisms, and more specifically mechanical movements.

SUMMARY OF THE INVENTION In carrying out my invention in a preferred embodiment, I provide a pair of flexible tension members wound on a drum biased to exert a tension on the members, the ends of the tension members remote from the drum being connected to the ends of a bar mounted for pivotal movement about an axis intermediate the ends thereof, and means for effectively varying the length of one of the tension members between the drum and the bar.

The objects, features and advantages of my invention will become apparent to persons skilled in the art when the following detailed description is taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary view of a lift truck embodying my invention,

FIG. 2 shows my invention in more detail with the operators station in both lowered and raised positions,

FIG. 3 is similar to FIG. 2 with the mechanism actuated to effectively shorten one of the tension members,

FIG. 4 is a view of the drum with a portion broken away,

FIG. 5 is a fragmentary view of the A control handle and bracket, and

FIG. 6 is a schematic drawing of a portion of the power and control circuitry for the lift truck'of FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I the reference numeral 10 denotes generally a portion of a lift truck which includes a pair of forwardly extending outrigger arms 12 that have a pair of wheels 14 mounted for rotation adjacent the forward ends thereof. Lift truck 10 also includes an extendible telescopic upright 16 to which a pair of forwardly extending load engaging fork arms 18 are connected for vertical movement. Also mounted on upright 16 for vertical movement is an operators station 20 which includes a platform 22 and a control console 24. At this point it will be seen that lift truck 10 is of the type which is generally known in the art as an order picker. That is, an operator rides on platform 24 and picks items out of various bins at varying elevations and loads them onto a pallet carried on fork arms 18. As upright 16 is extended the operator may be elevated to as much as 20 feet above floor level, and so it is highly desirable to have a simple safety mechanism readily available to the operator to shut off all power to lift truck 10 in case of a failure in one of the control circuits which might cause the truck to function in a dangerous manner.

In order to have a high degree of reliability for the safety mechanism it is desirable that as much of it as possible be of simple mechanical components to actuate a switch to cut off all power for the truck. This presents somewhat of a problem because it is necessary that the safety mechanism be extendible since the portion of the safety mechanism mountedon operator's station 20 may be elevated as much as 20 feet between its lowest and highest positions.

Referring now also to FIGS. 2 and 3, safety mechanism 26 will be described in detail. Safety mechanism 26 includes a rotary switch assembly 28 mounted on the body. 30 of lift truck ill. Switch assembly 28 includes a shaft 32 (FIG. 6) on which a bar 34 is mounted intermediate the ends thereof so that pivotal movement of bar 34 causes shaft 32 to rotate which in turn actuates switch assembly 28.

The rest of safety mechanism 26 is mounted on or carried by operators station 20 and includes a drum 36 mounted for rotation on control console 24 by means of a shaft 38. Drum 36 is biased in a clockwise direction, as viewed in FIGS. 1, 2 and 3, by means of a helical spring 40 (FIG. 4) connected between drum 36 and shaft 38.

Wound on drum 36 in the same direction and in side-by-side relation is a pair of flexible tension members 42 and 44 which may be, for example, steel tapes. The end of tension member 42 remote from drum 36 is connected to one end of bar 34 at 46 and the end of tension member 44 remote from drum 36 is connected to the other end of bar 34 at 48. At this point it will be seen that spring 40 serves to continually exert a tension on members 42 and 44 so that regardless of whether operator's station 20 is in the lowermost position or in an elevated position, as shown at 20', there is always an equal tension exerted on members 42 and 44.

' A roller or guide 50 is mounted for rotation on control console 24 by means of a shaft 52. Similarly, another roller or guide 54 is mounted for rotation on control console 24 by means of a shaft 56. Also mounted for rotation on shaft 56 is a support 58 on which a roller or guide 60 is mounted for rotation. As can be seen, tension member 42 is trained around opposite sides of rollers 54 and 60 and also trained around roller 50. Tension member 44, on the other hand, is merely trained around roller 54. At this point it will become apparent that when roller 60 is swung from the position shown in FIG. 2 to the position shown in FIG. 3 that the result will be to effectively shorten the length of tension member 42 extending between roller 54 and bar 34 and at the same time effectively lengthening the portion of tension member 44 extending between roller 54 and bar 34. As a result bar 34 will be pivoted from the position shown in FIG. 2 to the position shown in FIG. 3. Since, as pointed out hereinabove, the tension exerted on members 42 and 44 by spring 40 is always equal.

Connected to support 58 is a control rod or handle 62 which extends through an opening 64 in a bracket 66 connected to control console 24. A compression spring 68 is carried by rod 62 and is disposed between bracket 66 and a spring retainer 70 mounted on control rod 62. Control rod 62 also includes a notch 72 which is engageable with the edge of opening 64. Thus, when notch 72 engages the edge of opening 64 support 58 and roller 60 are in the position shown in FIG. 2. When rod 62 is pushed so as to disengage notch '72 from the edge of opening 64 the, bias of spring 68 causes support 58 and roller 60 to be pivoted in a clockwise direction to the position shown in FIG. 3, thereby pivoting bar 34 and actuating spring assembly 28. In addition, it is possible to actuate support 58 and roller 60 in a clockwise direction past the position shown in FIG. 3 by having the operator push downwardly on control rod 62, thereby pivoting bar 34 further in a clockwise direction to further actuate switch assembly 28.

Referring now to FIG. 6, the power and control circuitry for lift truck 10 will be described insofar as it relates to safety mechanism 26. A battery 74 has a pair of conductors 76 and 78 connected thereto, across which a drive motor 80, a pump motor 82 and various controls 84 for operating lift truck 10 are connected. Controls for operating lift truck 10 include, in addition to those indicated generally by reference numeral 84, a solenoid 86 which is arranged to be connected across conductors 76 and 78. Solenoid 86 is connected to a lowering valve 88 so that when solenoid 86 is energized valve 38 is actuated to lower the operators station 20 and load engaging forks 18 which are carried by upright 16.

As will be noted, switch assembly 28 includes an on-off switch 90 disposed in conductor 76, and on-off switch 92 disposed in conductor 76 between controls 84 and solenoid 36 and an on-off switch 94 disposed in a conductor 96 connected to conductor 76 to bypass switches 90 and 92, as shown. Switch assembly 28 is actuatable between three positions. In the first position switches 90 and 32 are closed and switch 94 is open. In the second position all three switches are open and in the third position switches 99 and 92 are open and switch 94 is closed. The obvious effect on the power and control circuits for lift truck 10 is that with switch assembly 28 in the first position the power from battery 74 can be supplied to motors 80 and 82 and controls 84 and solenoid 86 so that lift truck is fully operative. With switch assembly 28 in the second position thereof no power from battery 74 can be delivered to the motors, controls or solenoid so that it is not possible to operate the lift truck. With switch assembly 28 in the third position thereof it is possible to supply power only to solenoid 86 so that upright 16 can be lowered.

In order to enable persons skilled in the art to better understand my invention, I will now explain the operation of it. It will be assumed that an operator is standing on platform 22 and wishes to raise operators station to some indeterminate elevation indicated as 20 in FIG. 2. In order to do this controls 84 are manipulated to cause upright 16 to extend, thereby elevating operators station 20 together with load engaging forks 18. During elevation of operator's station 20 drum 36 will rotate in a counterclockwise direction, thereby paying out tension members 42 and 44 and at the same time continuing to exert a tension on them due to spring 40. Now, assuming controls 84 malfunction, for example, by having a set of motor speed contacters weld together so that lift truck 10 is being driven in a forward direction and the operator cannot stop the forward movement of the truck, the operator in order to stop truck 10 needs merely to push control rod 62 so as to disengage notch 72 from the edge of opening 64. When this occurs spring 68 will cause support 58 and roller 60 to be actuated to the position shown in FIG. 3. This causes, in effect, tension member 42 to shorten and tension member 44 to lengthen so that bar 34 is pivoted from the position shown in FIGS. 1 and 2 to the position shown in FIG. 3. This movement of bar 34 actuates switch assembly 28 from the first position thereof in which switches 90 and 92 are closed and switch 94 is open to the second position thereof in which switches 90, 92 and 94 are all open. As a result battery 74 is disconnected from all the power and control circuits so that, regardless of the malfunction in the electrical circuitry of lift truck 10, it will stop. In order to safely get down from an elevated position of operators station 20, the operator now pushes on control rod 62 to pivot support 58 and roller 60 further in a clockwise direction from the position shown in FlG. 3 which has the effect of further pivoting bar 34 in a clockwise direction to actuate switch assembly 28 to the third position thereof which results in switch 94 being closed so that power from battery 74 is supplied to solenoid 86. As pointed out previously, when solenoid 86 is energized it actuates valve 88 to lower upright 16. At this point it should be noted that switch 92 continues to be open so that there is no feed back of the current being up plied to solenoid 82 to the other controls 84.

While only a single embodiment of my invention has been described in detail, it will be understood that such description is illustrative only and that my invention is subject to various modifications and changes which fall within the scope and spirit of it. Consequently, the limits of my invention should be determined from the following appended claims.

Iclaim:

1. For use with a first member and a second member, one of the members being movable toward and away from the other member, the combination comprising a bar connected to the first member, the said bar being pivotal about an axis inter mediate the ends thereof, a drum mounted for rotation on the second member, first and second tension means wound on the said drum, the said first tension means having an end remote from the said drum connected to one end of the said bar and the said second tension means having an end remote from the said drum connected to the other end of the said bar, means connected to the said drum for biasing the said drum in the direction of rotation for'exerting a tension on both of the said tension means and means carried by the said second member and engagingone of the said tension means for effectively varying the'length of a portion of the said one tension means.

2. The combination as set forth in claim I wherein the said varying means includes a first guide mounted on the second member, a support mounted for pivotal movement between first and second positions on the second member and a second guide connected to the said support, and the said one tension means is trained around the said guides so that actuation of the said support between the said first and second positions varies the length of the said one tension means extending between the said drum and the said bar.

3. For use with a lift truck having a body, an extendible upright and an operators station mounted on the upright for vertical movement, a safety mechanism comprising first. switch means mounted on the body and actuatable to open or close, a bar mounted intermediate the ends thereof for pivotal movement between first and second positions and operatively connected to the said switch means so that the said switch means is closed when the said bar is in the said first position and open when the said bar is in the said second position, a drum mounted on the operators station for rotation, first and second tension means wound on the said drum, the end of the said first tension means remote from the said drum being connected to one end of the said bar and the end of the said tension means remote from the said drum being connected to the other end of the said bar, means biasing the said drum in the direction of rotation for exerting a tension on both of the said tension means and means mounted on the operator's station and engaging one of the said tension means for effectively varying a portion of the length of the said one tension means.

4. The mechanism as set forth in claim 3 wherein the said varying means includes a first guide mounted on the operators station, a support mounted for pivotal movement between first and second positions on the operators station and a second guide connected to the said support, and the said one tension means is trained around'the said guides so that actuation of the said support between the said first and second positions varies the length of the said one tension means extending between the said drum and the said bar.

5. The mechanism as set forth in claim 4 and including means connected to the said support for releasably holding the said support in the said first position and means connected to the said support for biasing the said support to the said second position.

6. For use with an electric lift truck having a body, an extendible upright, an operators station mounted on the upright for vertical movement, a power circuit connectable to a source of electric energy, a control circuit connectable to the source of electric energy, the control circuit including a solenoid, and an upright control valve connected to the solenoid so that when the solenoid is energized the valve is actuated to lower the upright, a safety mechanism comprising switch means mounted on the body, the said switch means being actuatable between a first position to connect the power and control circuits to the source of electric energy, a second position to disconnect the power and control circuits from the source of electric energy and a third position to connect the solenoid directly to the source of electric energy, a bar mounted intermediate the ends thereof for pivotal movement and operatively connected to the said switch means, a drum mounted for rotation on the operators station, first and second tension means wound on the said drum, the end of the said first tension means remote from the said drum being connected to one end of the said bar and the end of the said second tension means remote from the said drum being connected to the other end of the said bar, means biasing the said drum in the direction of rotation for exerting a tension on both of the said tension means and means mounted on the operators station and engaging one of the said tension means for effectively varying a portion of the length of the said one tension means so that the said switch means can be actuated to any one of the said three positions thereof by manipulation of the said varying means regardless of the extension of the upright.

7. The mechanism as set forth in claim 6 wherein the said varying means includes a first guide mounted on the operators station, a support mounted on the operators station for pivotal movement between fourth, fifth and sixth positions and a second guide connected to the said support, and the said one tension means is trained around the said guides so that when the said varying means is in the said fourth, fifth or sixth positions thereof that the said switch means is actuated to the said first, second or third positions, respectively.

8. The mechanism as set forth in claim 7 and including 

1. For use with a first member and a second member, one of the members being movable toward and away from the other member, the combination comprising a bar connected to the first member, the said bar being pivotal about an axis intermediate the ends thereof, a drum mounted for rotation on the second member, first and second tension means wound on the said drum, the said first tension means having an end remote from the said drum connected to one end of the said bar and the said second tension means having an end remote from the said drum connected to the other end of the said bar, means connected to the said drum for biasing the said drum in the direction of rotation for exerting a tension on both of the said tension means and means carried by the said second member and engaging one of the said tension means for effectively varying the length of a portion of the said one tension means.
 2. The combination as set forth in claim 1 wherein the said varying means includes a first guide mounted on the second member, a support mounted for pivotal movement between first and second positions on the second member and a second guide connected to the said support, and the said one tension means is trained around the said guides so that actuation of the said support between the said first and second positions varies the length of the said one tension means extending between the said drum and the said bar.
 3. For use with a lift truck having a body, an extendible upright and an operator''s station mounted on the upright for vertical movement, a safety mechanism comprising first switch means mounted on the body and actuatable to open or close, a bar mounted intermediate the ends thereof for pivotal movement between first and second positions and operatively connected to the said switch means so that the said switch means is closed when the said bar is in the said first position and open when the said bar is in the said second position, a drum mounted on the operator''s station for rotation, first and second tension means wound on the said drum, the end of the said first tension means remote from the said drum being connected to one end of the said bar and the end of the said tension means remote from the said drum being connected to the other end of the said bar, means biasing the said drum in the direction of rotation for exerting a tension on both of the said tension means and means mounted on the operator''s station and engaging one of the said tension means for effectively varying a portion of the length of the said one tension means.
 4. The mechanism as set forth in claim 3 wherein the said varying means includes a first guide mounted on the operator''s station, a support mounted for pivotal movement between first and second positions on the operator''s station and a second guide connected to the said support, and the said one tension means is trained around the said guides so that actuation of the said support between the said first and second positions varies the length of the said one tension means extending between the said drum and the said bar.
 5. The mechanism as set forth in claim 4 and including means connected to the said support for releasably holding the said support in the said first position and means connected to the said support for biasing the said support to the said second position.
 6. For use with an electric lift truck having a body, an extendible upright, an operator''s station mounted on the upright for vertical movement, a power circuit connectable to a source of electric energy, a coNtrol circuit connectable to the source of electric energy, the control circuit including a solenoid, and an upright control valve connected to the solenoid so that when the solenoid is energized the valve is actuated to lower the upright, a safety mechanism comprising switch means mounted on the body, the said switch means being actuatable between a first position to connect the power and control circuits to the source of electric energy, a second position to disconnect the power and control circuits from the source of electric energy and a third position to connect the solenoid directly to the source of electric energy, a bar mounted intermediate the ends thereof for pivotal movement and operatively connected to the said switch means, a drum mounted for rotation on the operator''s station, first and second tension means wound on the said drum, the end of the said first tension means remote from the said drum being connected to one end of the said bar and the end of the said second tension means remote from the said drum being connected to the other end of the said bar, means biasing the said drum in the direction of rotation for exerting a tension on both of the said tension means and means mounted on the operator''s station and engaging one of the said tension means for effectively varying a portion of the length of the said one tension means so that the said switch means can be actuated to any one of the said three positions thereof by manipulation of the said varying means regardless of the extension of the upright.
 7. The mechanism as set forth in claim 6 wherein the said varying means includes a first guide mounted on the operator''s station, a support mounted on the operator''s station for pivotal movement between fourth, fifth and sixth positions and a second guide connected to the said support, and the said one tension means is trained around the said guides so that when the said varying means is in the said fourth, fifth or sixth positions thereof that the said switch means is actuated to the said first, second or third positions, respectively.
 8. The mechanism as set forth in claim 7 and including means connected to the said support for releasably holding the said support in the said fourth position and means connected to the said support for biasing the said support to the said fifth position. 